The present invention relates to video signal processing, and more particularly relates to the processing of such signals to embed auxiliary data (e.g. identification or control data therein), and the subsequent extraction and use of such data.
The copying and redistribution of commercial imagery and video productions has long been a cause of lost revenues to the creators/producers of such material. The advance of technology has not only expanded the means of legitimate distribution for visual/video works, but has also made it easier to copy these materials for unauthorized purposes.
Various methods have been developed to eliminate or limit both sophisticated and unsophisticated illegitimate distribution. Some of these methods rely on physical means. Others employ a xe2x80x9cdon""t copy signalxe2x80x9d to disable a machine""s recording function.
In accordance with preferred embodiments of the present invention, a control message (sometimes termed a xe2x80x9cdigital watermarkxe2x80x9d) is embedded directly into an audio signal by adding a low-level signal that carries the control message. Hardware or software systems can then read this control message and, for example, disable recording functions if so instructed.
Key practical issues are addressed whereby the perceptual impact of this added message can be adjustedxe2x80x94both overall and as a function of the underlying visual and audio content. For example, a blank video sequence ought in general to have minimal visible effects, whereas active motion scenes with various areas of high detail can generally tolerate more visual energy in a watermark. Similarly, quieter or lower entropy segments of audio ought to have minimal audible effects, whereas louder or higher entropy segments can generally tolerate more energy in an audio watermark.
Methods are further detailed whereby the embedded message can survive lossy compression processes. An example of a lossy compression process is the MPEG video and audio compression standard. (MPEG is commonly employed when video and audio is distributed in digital form, e.g. on optically encoded disks.)